1. Field of the Invention
This invention relates to a releasable compression device for use on a rolling or crushing mill and more particularly to a device which maintains a constant crushing pressure on crushing rolls of the mill while at the same time allowing one of the rollers to pivot outwardly to allow a passage of a foreign object if such is encountered.
2. Description of the Prior Art
A rolling or crushing mill for processing such hard materials as Carborundum into a finely controlled particle size has been available and known in the art for some time. Particle size of the material processed by such a mill is controlled by the dimension of the nip formed between the crushing rollers.
It has been customary in such a mill to have one roller fixed in location while a second roller is supported in a pivotable frame which allows adjustment of the nip dimension as well as a momentary increase in the nip dimension in case the supply of raw material includes a foreign object which cannot be crushed and could cause damage to the surface of the rollers if the nip were not expandable.
Initial adjustment of the nip between the rollers has been perfected by providing a pivotanble support frame fo the adjustable roller with a lever arm which is carried between two adjustable nuts on a threaded rod. By adjusting the position of the lower nut and then tightening the upper nut accordingly, the relative position of the pivotable roller is maintained to establish the desired dimension of the nip between the fixed and adjustable roller. Any force tending to increase the nip dimension is resisted by the structure of the mill.
Under these conditions, the only safety feature against overstress of the structure because of a change in conditions of the raw material entering the crusher or upon entry of a foreign body into the roller nip, is the strength of the individual components of the mill.
As an added safety feature, some mills use a breakaway or hinge bearing which fails at a certain stress point.
Additionally, hydraulic supporting devices have been incorporated for use with a rolling or crushing mill to position the adjustable roller and thereby control the dimension of the nip. Examples of such a device are disclosed in German Specification No. 1,584,592. Also, German Patent No. 946,676 discloses a controllable hydraulic pressure apparatus for a roller or crushing mill in which a friction bar is incorporated with the roller. German Patent No. 1,083,104 also discloses a hydraulic pressure apparatus for a roller or a crusher mill about which a spring loaded pressure adjusted valve apparatus is incorporated to regulate the operating pressure of the rollers.